1. Field of the Invention
This invention relates to a camera designed for a film unit having film, a cartridge containing the film therein, and an information recording portion on which particular information is recorded.
2. Related Background Art
Cameras of this type have heretofore been disclosed in U.S. Pat. Nos. 4,860,037 and 4,864,332. The cameras disclosed in these patents are both fit for a film unit in which a magnetic recording portion is provided on the leader portion of film. When this film unit is loaded into such camera and photographing is effected and a midroll interrupt operation for taking out the film unit from the camera before all the frames of the film are exposed is applied to the camera, rewinding of the film is started. During this rewinding, information regarding the number of exposed frames is recorded on said magnetic recording portion through a magnetic head disposed in the film feeding path of the camera. When the film unit in which said information has been recorded on the magnetic recording portion is again loaded into the camera, the winding of the camera is started. During this winding, the information regarding the number of exposed frames recorded on the information recording portion through the magnetic head is read out. This winding is controlled in conformity with the read-out information regarding the number of exposed frames, and is stopped when an unexposed frame to be exposed next time is brought to a photographing position opposed to a photo-taking lens. Thereafter, photographing can be continued from that unexposed frame. When the information to the effect that all frames have been exposed is read out from the information recording portion, the film is rewound into the cartridge for the purpose of double exposure prevention and the photographing operation is inhibited from being effected and at the same time, a warning to that effect is given. Both of these cameras are so-called ordinary wind mode cameras in which photographing is effected from the frame most adjacent to the leader portion of the film.
U.S. Pat. No. 4,878,075 also discloses a camera which performs a similar function. However, a film unit fit for this camera has its magnetic recording portion provided near each frame of film. In this camera, each, time a frame is exposed, the information to the effect that that frame has been exposed is recorded on the magnetic recording portion by a magnetic head. This camera is a so-called prewind mode camera in which after all frames have once been wound, photographing is effected from the frame which is most adjacent to the distal end portion side of the film (the magazine shaft side in the cartridge) and one frame is rewound each time photographing is completed. Therefore, when the film unit is once taken out of the camera and then is reloaded into the camera, the camera reads out the information on the magnetic recording portion by the magnetic head while winding the film, and when the information to the effect that the frame is an exposed frame is read out, that is, when the frame exposed last before the film unit is taken out of the camera is detected, the winding is stopped. Subsequently, rewinding is started and an unexposed frame neighboring said exposed frame is transported to the photographing position, whereupon the rewinding is stopped. Thereafter, photographing can be continued from said unexposed frame. Where all frames are exposed frames, rewinding is started when the exposed frame most adjacent to the leader portion is detected. When in the process of this rewinding, the leader portion of the film breaks off its contact with a film presence detecting switch provided in the feeding path of the camera, a warning operation is started by the output of this switch conforming to this. The rewinding is stopped after a predetermined time has elapsed from the output of said switch.
All of the above-described cameras according to the prior art have the advantage that it is readily possible to expose up to a midroll frame and continue to expose the film which has once been taken out, but this is an advantage that can be realized only when a film unit in which information recording has been effected in the same wind mode and in the same form is reloaded into the camera. It is impossible to continue photographing when film exposed in a wind mode differing from that of such cameras is reloaded.
Also, when the midroll interrupt operation of the film is performed several times, data is overwritten on the same position of the magnetic recording portion by the same number of times. As a result, when previous data cannot be completely erased, wrong data may be undesirably read out upon a reproduction of the data. In particular, when data is recorded by a magnetic head, if a recording position is offset, crosstalk with the already recorded data undesirably occurs.